If you need something EZConfig doesn't provide, see the
hackage X11 package page has links to the current Types and ExtraTypes.* modules where keysyms are defined. Types contains the basics, media keys are in ExtraTypes.XF86, and
international keyboard symbols are in Extra.Types.XorgDefault

You can also search in /usr/include/X11/keysymdef.h and lower-case the first character (XK* becomes xK*).